Whatever Happened To Archimedes?

Science bleg posed to someone who follows global warming theory: Stipulating for the moment that everything the warmenists say about greenhouse gases is true, why would the oceans rise rather than recede?
  • Why would melting ice at the poles cause the seas to rise? The ice is already in the water, right, so its volume would actually contract slightly with melting?
  • Is it projected glacier run-off we're threatened by? Wouldn't higher global temperatures cause water to evaporate at a faster rate, causing drought rather than flood? Some special I watched claimed the peoples of five nations whose water supply is fed by glaciers in the Himalayas are already threatened by drought. Where's all this water coming from?
I never knew much about science and have forgotten what I once knew, so I'm asking. If the theory were true, what is supposed to be happening that's going to cause the oceans to rise?